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1 The e ects of endothelin (ET)-1 1 ± 31 and ET-2 1 ± 31 , human chymase products of the corresponding big ETs, on the intracellular free Ca 2+ showed that both ET A -and ET B -receptors at the ratio of 4 : 1 were expressed on BSMC. ET-1 1 ± 31 , big ET-1 and ET-2 1 ± 31 inhibited [ 125 I]-ET-1 binding in a concentration-dependent manner, and these e ects were attenuated by treatment with thiorphan. On the other hand, big ET-2 slightly inhibited the binding at a high concentration and this was not a ected by thiorphan. 5 These results suggest that ET-1 1 ± 31 , big ET-1 and ET-2 1 ± 31 cause an increase in [Ca 2+ ] i by being converted into the corresponding ET-1 and ET-2 by NEP, but this did not occur with big ET-2 in human BSMC. ET-2 1 ± 31 produced by human chymase from big ET-2 might be important for the generation of ET-2 in human bronchial tissue.